TW202104295A - Modified vinyl alcohol-based polymer, and dispersion stabilizer for suspension polymerization - Google Patents

Abstract

Provided is a modified vinyl alcohol-based polymer that is useful for obtaining a resin having characteristics such as having few coarse particles among resin particles. This modified vinyl alcohol-based polymer has a portion represented by general formula (I). This portion has a polyoxyalkylene unit bonded to a poly(vinyl alcohol) chain via an ether bond and/or a carbon-carbon bond only; and an organic acid unit bonded to a poly(vinyl alcohol) chain. The ratio of the number of moles of the monomer unit bonded to the polyoxyalkylene unit relative to the total number of moles of monomer units that constitute poly(vinyl alcohol) chains in the modified alcohol-based polymer is 0.01-5 mol%. The ratio of the number of moles of the organic acid unit relative to the total number of moles of monomer units that constitute poly(vinyl alcohol) chains in the modified vinyl alcohol-based polymer is 0.1-10 mol%.

Description

Modified vinyl alcohol polymer and its manufacturing method, dispersion stabilizer for suspension polymerization, and vinyl resin manufacturing method

The present invention relates to a modified vinyl alcohol polymer. In addition, the present invention relates to a dispersion stabilizer for suspension polymerization, and particularly relates to a dispersion stabilizer suitable for suspension polymerization of vinyl compounds represented by vinyl chloride.

In the case of suspension polymerization of vinyl chloride monomers or a mixture of vinyl chloride monomers and monomers that can be copolymerized with the vinyl chloride monomers, various dispersion stabilizers must be used, such as polyvinyl alcohol and hydroxymethyl Among the dispersion stabilizers such as cellulose and gelatin, polyvinyl alcohol (hereinafter also referred to as "PVA") has excellent properties and is most commonly used. For example, a method of using a modified PVA having a specific oxyalkylene group in its side chain as a dispersion stabilizer for suspension polymerization of an ethylene-based compound has been proposed (see Patent Document 1 to Patent Document 3).

(式中，R1表示氫原子或甲基，R2表示氫原子或碳數1至8之烷基。m及n分別表示氧伸烷基單元之重複單元數，為1≤m≤10、3≤n≤20)。Patent Document 1 discloses a dispersion stabilizer for suspension polymerization of a vinyl compound, which contains: polyoxyalkylene modified vinyl alcohol copolymer (A), which contains a side chain represented by the following general formula The polyoxyalkylene vinyl alcohol polymer has an average polymerization degree of viscosity of 600 to 5000, and a saponification degree of 60 mol% or more. The modified mass of polyoxyalkylene polymer is 0.1 mol% to 10 mol%.

(In the formula, R1 represents a hydrogen atom or a methyl group, and R2 represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. m and n represent the number of repeating units of the oxyalkylene unit, respectively, and are 1≤m≤10, 3≤ n≤20).

In Patent Document 1, the effect obtained by the dispersion stabilizer is described as follows. When the dispersion stabilizer is used in the suspension polymerization of a vinyl compound, it is added in a small amount to impart high polymerization stability. Thereby, agglomeration or scale adhesion caused by polymerization instability is reduced, and ethylene-based polymer particles having a narrow particle size distribution and a high volume specific gravity with few coarse particles can be obtained.

Patent Document 2 discloses a dispersion stabilizer for suspension polymerization, which contains: a polyoxyalkylene-modified vinyl alcohol polymer (A), which has an alkylene group with a carbon number of 2 to 4 in the side chain and repeats A polyoxyalkylene group having a unit number of 2 to 100; and the polyoxyalkylene-modified vinyl alcohol polymer (A) has an average degree of polymerization of less than 500, a degree of saponification greater than 70 mol%, and a polyoxyalkylene modified vinyl alcohol polymer (A). The oxyalkylene modification rate is 0.1 mol% or more and 10 mol% or less.

(式中，R¹ 及R² 均為氫原子，或者任一個為甲基且另一個為氫原子，R³ 及R⁴ 中任一個為甲基或乙基，另一個為氫原子，R⁵ 表示氫原子或碳數1至8之烷基。m及n分別表示氧伸烷基單元之重複單元數，為1≤m≤50、1≤n≤50)。In Patent Document 2, as the aforementioned polyoxyalkylene group, a polyoxyalkylene group represented by the following general formula is disclosed.

(In the formula, R ¹ and R ² are both hydrogen atoms, or either one is a methyl group and the other is a hydrogen atom, either of R ³ and R ⁴ is a methyl group or an ethyl group, and the other is a hydrogen atom, R ⁵ It represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. m and n respectively represent the number of repeating units of the oxyalkylene unit, and are 1≤m≤50, 1≤n≤50).

In Patent Document 2, the effect obtained by the dispersion stabilizer is described as follows. When the dispersion stabilizer is used for suspension polymerization of vinyl compounds, the polymerization stability is high, so the formation of coarse particles is small, and particles with uniform particle size can be obtained. Furthermore, agglomeration or adhesion of scales caused by polymerization instability is reduced, and polymer particles with excellent plasticizer absorption and demonomerization properties can be obtained.

(式中，R¹ 、R² 表示氫原子或烷基，n表示0或正整數，X表示氫原子、烷基、烷基醯胺基、烷基酯基中的任一個)。Patent Document 3 discloses a dispersion stabilizer characterized in that it is composed of a partially saponified polyvinyl alcohol-based resin, the partially saponified polyvinyl alcohol-based resin has a saponification degree of 65 to 85 mol%, and contains 0.1% in the side chain. mol% to 10 mol% of alkylene oxide, and iodine has a color value of 0.3 or more. According to Patent Document 3, the oxyalkylene group is represented by the following general formula.

(In the formula, R ¹ and R ² represent a hydrogen atom or an alkyl group, n represents 0 or a positive integer, and X represents any one of a hydrogen atom, an alkyl group, an alkylamido group, and an alkyl ester group).

In Patent Document 3, the effect obtained by the dispersion stabilizer is described as follows. Compared with the previous product, even in suspension polymerization using a buffer (agent), the protective colloid is not reduced, and the polymerization stability is good. The resulting vinyl polymer has a plasticizer absorption and fish eye (fish eye). ) Has good performance such as attenuation speed, and does not generate coarse particles of ethylene polymer. [Prior Technical Literature] [Patent Literature]

[Patent Document 1] International Publication No. 2010/113569. [Patent Document 2] International Publication No. 2013/115239. [Patent Document 3] Japanese Patent Application Laid-Open No. 2004-075870.

[The problem to be solved by the invention]

Generally, the suspension polymerization of vinyl chloride is carried out in batches. Specifically, it is a method of feeding an aqueous medium, a dispersion stabilizer, a polymerization initiator, and a vinyl chloride monomer into a polymerization tank, and adding necessary additives, and then gradually raising the temperature to the polymerization temperature to perform the reaction. However, this method requires a very long time for feeding and heating. Sometimes only feeding and heating account for more than 10% of the polymerization time of one cycle. Therefore, it becomes a reason for the decrease in the productivity of the polymer, which has become the industry for many years. Unresolved issues. However, various methods have been studied in order to solve this problem, and a warm water feed polymerization method (hot water charge method) using warm water above 40°C is proposed, which shortens the steps and time during polymerization. The aspect shows a big effect. In addition, in recent years, in areas with high temperatures such as Southeast Asia, the production of vinyl chloride resin has been actively carried out due to the increase in infrastructure needs, and the use of warm water above 40°C has been increasing.

However, the dispersion stabilizer described in Patent Document 1 to Patent Document 3 not only precipitates a part of polyvinyl alcohol when warm water is supplied, makes the aqueous solution cloudy and cannot exert its original excellent effect as a dispersion stabilizer, but also sometimes affects vinyl chloride The polymerization stability of the monomer and the physical properties of the resin cause adverse effects. Specifically, the following drawbacks are generated: (1) The produced vinyl chloride resin particles have fewer coarse particles; (2) Resin particles with uniform particle size can be obtained as much as possible to prevent the adhesion of scales; (3) As a result, the resin with high bulk density can improve the required performance such as molding processability during the processing of vinyl chloride to obtain the required performance.

Therefore, one of the problems of the present invention is to provide a modified vinyl alcohol polymer suitable as a dispersion stabilizer for suspension polymerization, which can be used in the suspension polymerization of vinyl chloride-based vinyl compounds using warm water above 40°C. The operability of the warm water feeding polymerization method, etc., is excellent, and fully meets the requirements of (1) to (3) above. [Means to solve the problem]

In order to solve the above-mentioned problems, the inventors of the present invention have conducted intensive studies and found that the following modified vinyl alcohol polymer is effective as a dispersion stabilizer for suspension polymerization of vinyl compounds. The modified vinyl alcohol polymer With a modification rate of 0.01 mol% to 5 mol%, it has a predetermined polyoxyalkylene unit (hereinafter referred to as "alkylene modification group"), and a modification rate of 0.1 mol% to 10 mol% has a predetermined polyoxyalkylene unit Organic acid unit.

(式中，R₁ 及R₂ 分別獨立為甲基或乙基或氫原子，R₃ 為烷基或氫原子。n表示重複單元數，為5≤n≤70之整數)。 [2]如[1]所記載之改質乙烯醇系聚合物，其中前述聚氧伸烷基單元之至少一部分具有通式(II)所示之部分。

(式中，R₁ 、R₂ 、R₃ 如[1]所記載。R₄ 及R₅ 中一個為甲基或乙基，另一個為氫原子。m表示重複單元數，為1≤m≤30之整數。其中，重複單元數n之部分與重複單元數m之部分不同)。 [3]如[1]或[2]所記載之改質乙烯醇系聚合物，其中有機酸單元具有羧酸酯。 [4]如[1]至[3]中任一項所記載之改質乙烯醇系聚合物，黏度平均聚合度為500至4000，皂化度為70mol%以上。 [5]一種懸浮聚合用分散穩定劑，係含有如[1]至[4]中任一項所記載之改質乙烯醇系聚合物。 [6]一種乙烯系樹脂之製造方法，係包含：使用如[5]所記載之懸浮聚合用分散穩定劑，使乙烯系化合物單體、或者乙烯系化合物單體和可與該乙烯系化合物單體共聚合之單體的混合物分散於水中，進行懸浮聚合。 [7]一種改質乙烯醇系聚合物之製造方法，係製造如[1]至[4]中任一項所記載之改質乙烯醇系聚合物，包含下述步驟：使乙烯酯系單體於不飽和有機酸之共存下，與具有前述聚氧伸烷基單元之不飽和單體共聚合，獲得改質乙烯酯系聚合物。 [發明功效]Therefore, the present invention is exemplified below in one aspect. [1] A modified vinyl alcohol-based polymer having: polyoxyalkylene units, having a part represented by the general formula (I), and this part is only connected to polyethylene via ether bonds and/or carbon-carbon bonds The alcohol chain is bonded; the organic acid unit is bonded to the polyvinyl alcohol chain; relative to the total number of moles of monomer units constituting the polyvinyl alcohol chain of the modified vinyl alcohol polymer, it is the same as the aforementioned polyoxyalkylene The ratio of the molar number of the aforementioned monomer units to which the unit is bonded is 0.01 mol% to 5 mol%, and relative to the total molar number of the monomer units constituting the polyvinyl alcohol chain of the modified vinyl alcohol polymer, the organic The ratio of the number of moles of acid units is 0.1 mol% to 10 mol%.

(In the formula, R ₁ and R ₂ are each independently a methyl group or an ethyl group or a hydrogen atom, and R ₃ is an alkyl group or a hydrogen atom. n represents the number of repeating units, and is an integer of 5≤n≤70). [2] The modified vinyl alcohol polymer as described in [1], wherein at least a part of the polyoxyalkylene unit has a part represented by the general formula (II).

(In the formula, R ₁ , R ₂ , and R _{3 are} as described in [1]. One of R ₄ and R ₅ is a methyl group or an ethyl group, and the other is a hydrogen atom. m represents the number of repeating units, and is 1≤m≤ An integer of 30. The part of the number of repeating units n is different from the part of the number of repeating units m). [3] The modified vinyl alcohol polymer as described in [1] or [2], wherein the organic acid unit has a carboxylic acid ester. [4] The modified vinyl alcohol polymer as described in any one of [1] to [3], the viscosity average polymerization degree is 500 to 4000, and the saponification degree is 70 mol% or more. [5] A dispersion stabilizer for suspension polymerization, comprising the modified vinyl alcohol polymer as described in any one of [1] to [4]. [6] A method for producing a vinyl resin, comprising: using the dispersion stabilizer for suspension polymerization as described in [5] to make a vinyl compound monomer, or a vinyl compound monomer, and the vinyl compound monomer The mixture of monomers of bulk copolymerization is dispersed in water for suspension polymerization. [7] A method for producing a modified vinyl alcohol-based polymer, which is to produce the modified vinyl alcohol-based polymer as described in any one of [1] to [4], comprising the following steps: making a vinyl ester-based monomer Under the coexistence of an unsaturated organic acid, it is copolymerized with the unsaturated monomer having the aforementioned polyoxyalkylene unit to obtain a modified vinyl ester polymer. [Efficacy of invention]

When the dispersion stabilizer for suspension polymerization of the present invention is used for suspension polymerization of vinyl compounds, the formation of coarse particles is small, and resin particles with high uniformity in particle size can be obtained. Furthermore, the formation of coarse particles is small, so the agglomeration during polymerization is suppressed, and particles with high particle size uniformity can be obtained, so that the adhesion of scales is reduced. In addition, resins with high bulk density can be obtained, and the productivity during resin processing is improved. In addition, even in the warm water feeding polymerization method (hot water feeding method) using warm water above 40°C or in areas where the average temperature is high, the dispersant can be used without impairing its original performance. In this way, the dispersion stabilizer for suspension polymerization of the present invention can have the required performance that is difficult to achieve with the prior art.

In one embodiment, the dispersion stabilizer for suspension polymerization of the present invention contains a modified vinyl alcohol polymer (hereinafter also referred to as "modified PVA"), and the modified PVA has: polyoxyalkylene units, It has the part represented by the general formula (I), which is only bonded to the polyvinyl alcohol chain via ether bonds and/or carbon-carbon bonds; and the organic acid unit is bonded to the polyvinyl alcohol chain.

(式中，R₁ 及R₂ 分別獨立為甲基或乙基或氫原子，R₃ 為烷基或氫原子。n表示重複單元數，為5≤n≤70之整數)。General formula (I):

(In the formula, R ₁ and R ₂ are each independently a methyl group or an ethyl group or a hydrogen atom, and R ₃ is an alkyl group or a hydrogen atom. n represents the number of repeating units, and is an integer of 5≤n≤70).

n is preferably 10 or more, more preferably 15 or more, and even more preferably 20 or more. In addition, n is preferably 70 or less, more preferably 60 or less.

(式中，R₁ 及R₂ 分別獨立為甲基或乙基或氫原子，R₃ 為烷基或氫原子。n表示重複單元數，為5≤n≤70之整數。R₄ 及R₅ 中一個為甲基或乙基，另一個為氫原子。m表示重複單元數，為1≤m≤30之整數。其中，重複單元數n之部分與重複單元數m之部分不同)。At least a part of the above-mentioned polyoxyalkylene unit preferably has two or more different parts as shown in the general formula (II). It is more preferable that the above-mentioned polyoxyalkylene units all have two or more different oxyalkylene moieties as shown in the general formula (II). As the two or more parts represented by the general formula (II), specific examples include: the part of the number of repeating units m is oxybutylene (R ₄ or R ₅ is an ethyl group, and the other is a hydrogen atom), and the number of repeating units The part of n is an oxyethylene group (R ₁ and R ₂ are both hydrogen atoms); or the part of the number of repeating units m is an oxyethylene group (R ₄ or R ₅ is a methyl group, and the other is a hydrogen atom), repeat The part of the unit number n is an ethylene oxide (R ₁ and R ₂ are both hydrogen atoms). Here, the part where the number of repeating units is m and the part where the number of repeating units is n are in any form of random arrangement and block arrangement, but it is easier to express from the viewpoint of the physical properties of the alkylene-modified group In other words, the block arrangement is preferred.

(In the formula, R ₁ and R ₂ are each independently a methyl group or an ethyl group or a hydrogen atom, and R ₃ is an alkyl group or a hydrogen atom. n represents the number of repeating units and is an integer of 5≤n≤70. R ₄ and R ₅ One of them is a methyl group or an ethyl group, and the other is a hydrogen atom. m represents the number of repeating units and is an integer of 1≤m≤30. The part of the number of repeating units n is different from the part of the number of repeating units m).

m is preferably 3 or more, more preferably 5 or more. In addition, m is preferably 25 or less, more preferably 20 or less.

The alkyl group representing R ₃ can be, for example, an alkyl group having 1 to 10 carbon atoms, preferably an alkyl group having 1 to 5 carbon atoms, and more preferably an alkyl group having 1 to 3 carbon atoms. Specific examples of the alkyl group representing R ₃ include methyl, ethyl, n-propyl, and isopropyl.

The parts represented by the general formula (I) and the general formula (II) are bonded to the polyvinyl alcohol chain only via the ether bond and/or the carbon-carbon bond, respectively, to prevent detachment due to changes in pH and fail to exert performance. It's appropriate in terms of point of view.

Examples of organic acid units in the above-mentioned modified PVA include: unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, and maleic acid, and salts of these acids, as well as dimethyl maleate and maleic acid Unsaturated carboxylic acid alkyl esters such as methyl esters. Furthermore, unsaturated sulfonic acids such as vinyl sulfonic acid, allyl sulfonic acid, and methallyl sulfonic acid, salts of these acids, unsaturated sulfonic acid esters, and the like can also be cited. The modified PVA may have one type of organic acid unit or two or more types of organic acid unit.

In the modified PVA of the present invention, the organic acid unit is not particularly limited. It is preferably an unsaturated carboxylic acid ester that generates a double bond in the polymer during saponification and drying that can exhibit reactivity during the polymerization of vinyl compounds. .

Although the above-mentioned modified PVA also depends on the type of alkylene-modifying group, it is important that the alkylene-modification rate is from 0.01 mol% to 5 mol%. If the alkylene modification rate exceeds 5 mol%, the balance of the hydrophilic and hydrophobic groups contained in each molecule of the modified PVA will not be maintained, and the water solubility of the modified PVA will decrease or its affinity with respect to vinyl compound monomers It is difficult to use as a dispersion stabilizer for suspension polymerization due to its deterioration. Therefore, it is important that the alkylene modification rate is 5 mol% or less, preferably 4 mol% or less, and more preferably 2 mol% or less. On the other hand, when the alkylene modification rate is less than 0.01 mol%, although the water solubility is excellent, the number of modifying groups contained in the modified PVA is small, and the required physical properties are not sufficiently expressed. Therefore, it is important that the alkylene modification rate is 0.01 mol% or more, preferably 0.05 mol% or more, and more preferably 0.1 mol% or more.

The so-called alkylene modification rate refers to the total number of moles of monomer units constituting the polyvinyl alcohol chain of the modified PVA, and is bound to the polyoxyalkylene unit having the part represented by the above general formula (I) The ratio of the number of moles of the aforementioned monomer units bound (mol%). The alkylene modification rate can be obtained by proton NMR (Nuclear magnetic resonance; nuclear magnetic resonance). Specifically, after the modified PVA is saponified to a saponification degree of 99.95 mol% or more, it is thoroughly washed with methanol to produce a modified PVA for analysis. The prepared modified PVA for analysis was dissolved in heavy water, and a few drops of NaOH heavy aqueous solution were added dropwise to adjust the pH to 14, and then measured at 80°C using proton NMR. When calculating based on the oxygen ethylene moiety (for example, R ₁ ＝H, R ₂ ＝H), it is based on the integral of the 1.2 ppm to 1.8 ppm peak attributable to the methylene group of the polyvinyl alcohol chain of the modified PVA The value and the integrated value of the 3.6 ppm to 3.7 ppm peak attributable to the oxyethylene moiety are calculated by conventional methods. Specifically, if the integral value of the methylene group of the polyvinyl alcohol chain of the modified PVA is set to b, the integral value of the oxyethylene part is set to a, and the number of repeating units of the oxyethylene part is set to x, compared with the number of protons (2H for methylene and 4H for ethylene), the modification rate is calculated as {a/(4×x)}/(b/2)×100 (mol%). For example, when a=1, x=1, and b=100, the modification rate is calculated to be 0.5 mol%. In addition, when the calculation is based on the oxybutylene or oxypropylene moiety, it is based on the integral value of the 1.2 ppm to 1.8 ppm peak attributable to the methylene group of the polyvinyl alcohol chain of the modified PVA, and the Oxypropylene moiety (R ₁ =H, R ₂ =CH ₂ CH ₃ (or R ₁ =CH ₂ CH ₃ , R ₂ ═H)) or oxypropylene moiety (R ₁ =H, R ₂ ＝CH ₃ (or R ₁ ＝CH ₃ , R ₂ ＝H)) The integral value of the 0.80 ppm to 0.95 ppm peak of the terminal methyl group, and the content is calculated by a conventional method. Specifically, if the integral value of the methylene group of the polyvinyl alcohol chain of the modified PVA is set to b, the integral value of the oxybutylene portion or the oxypropylene portion is set to c, and the number of repeating units is set to y, compared with the number of protons (methylene group is 2H, methyl group is 3H), the modification rate is calculated as {c/(3×y)}/(b/2)×100 (mol%). For example, when c=1, y=1, and b=100, the modification rate is calculated to be 0.67 mol%. Furthermore, when the modified PVA has both an oxyethylene moiety, an oxyethylene moiety or an oxyethylene moiety, compared to the alkylene modification rate calculated from the oxyethylene moiety , The alkylene modification rate calculated based on the integral value of the peak attributable to the oxypropylene moiety or the terminal methyl group of the oxybutylene moiety has a high measurement accuracy, so when there is a difference between the two values , The alkylene modification rate calculated based on the integral value of the peak of the terminal methyl group attributable to the oxypropylene moiety or the oxybutylene moiety.

In addition, the organic acid modification rate of the above-mentioned modified PVA must be 0.1 mol% to 10 mol%. When the organic acid modification rate is less than 0.1 mol%, it is difficult to maintain the tipping point above 40°C, or the starting point of the unsaturated double bond derived from the carbonyl group is reduced. As a result, a vinyl resin with an appropriate particle size cannot be obtained. In addition, it becomes an ethylene-based resin with a low bulk density. Therefore, the organic acid modification rate must be 0.1 mol% or more, preferably 0.3 mol% or more, and more preferably 0.5 mol% or more. In addition, when the organic acid modification rate exceeds 10 mol%, the physical properties are greatly changed due to the change in pH. Therefore, the protective colloid properties of polyvinyl chloride may be reduced during polymerization, or it may become chemically unstable and insoluble. Or gelation. Therefore, the organic acid modification rate must be 10 mol% or less, preferably 8 mol% or less, and more preferably 4 mol% or less.

The so-called organic acid modification rate is the ratio (mol%) of the number of moles of organic acid units to the total number of moles of monomer units constituting the polyvinyl alcohol chain of the modified PVA. The method for obtaining the modification rate of organic acid is not particularly limited, and it can be obtained by acid value, etc., but it is simply obtained by proton NMR. Specifically, after the modified PVA is completely saponified to a saponification degree of 99.95 mol% or more, it is washed with methanol sufficiently to produce modified PVA for analysis. The prepared modified PVA for analysis was dissolved in heavy water, and a few drops of NaOH heavy aqueous solution were added dropwise to adjust the pH to 14, and then measured at 80°C to obtain a ¹ H-NMR spectrum. It is calculated based on the integrated value of the peak of the methylene group (1.2ppm to 1.8ppm) of the polyvinyl alcohol chain of the modified PVA. For example, when the organic acid unit has a carboxyl group, it is calculated from the peak of 2.2 ppm to 2.9 ppm which is the hydrogen atom of the carbon adjacent to the carboxyl group. In addition, when the organic acid unit has a sulfonyl group, it is calculated from 2.8 ppm to 3.2 ppm which is the peak of the hydrogen atom attributable to the carbon adjacent to the sulfonic acid. Take the case where the organic acid unit has a carboxyl group as an example. If the integral value of the methylene group of the polyvinyl alcohol chain of the modified PVA is set to b, and the integral value of the hydrogen atom of the carbon adjacent to the carboxyl group is set to a, then compare Based on the number of protons (methylene is 2H), the modification rate is calculated as a/(b/2)×100 (mol%). For example, when a=1 and b=100, the modification rate is calculated to be 2.0 mol%.

In order to improve the dispersion stability when the vinyl compound is subjected to suspension polymerization, the viscosity average polymerization degree of the modified PVA is preferably 500 or more, more preferably 600 or more. In addition, in order to prevent the viscosity of the aqueous solution from increasing and the operation becoming difficult, the viscosity average polymerization degree of the modified PVA is preferably 4000 or less, more preferably 2000 or less, still more preferably 1500 or less, and even more preferably 1000 or less.

The viscosity average degree of polymerization is measured in accordance with JIS (Japanese Industrial Standards) K6726:1994. That is, after the modified PVA is completely saponified and purified, it is obtained from the limiting viscosity [η] measured in water at 30°C or in DMSO (Dimethyl sulfoxide; dimethyl sulfoxide).

In order to improve the water solubility and the tipping point for easy operation, the saponification degree of the modified PVA is preferably 70 mol% or more. In addition, in order to increase the porosity of the particles obtained when the ethylene-based compound is subjected to suspension polymerization and improve the absorption of the plasticizer, the saponification degree of the modified PVA is preferably 99.9 mol% or less, more preferably 90 mol% or less, More preferably, it is 80 mol% or less.

The degree of saponification of modified PVA is measured in accordance with JIS K6726:1994. That is, sodium hydroxide can be used to quantify the remaining acetic acid groups (mol%) in the sample and subtract it from 100 to obtain the degree of saponification of the modified PVA.

The manufacturing method of the modified PVA of the present invention is not particularly limited. For example, a method of grafting the hydroxyl group of PVA with polyoxyalkylene and organic acid can be used. Among them, the following method is easy and economical and can be used preferably. The method is to combine vinyl ester monomers represented by vinyl acetate in the coexistence of unsaturated organic acids with polyoxyalkylene units. The step of copolymerizing unsaturated monomers (having a part represented by the general formula (I)) to obtain a modified vinyl ester polymer; and saponifying the obtained modified vinyl ester polymer.

(通式(III)中，R₁ 、R₂ 、R₃ 、R₄ 、R₅ 、m、n與上述通式(II)相同)。Examples of the unsaturated monomers that derive the modified structure represented by the general formula (I) include: polyoxyalkylene alkenyl ether, polyoxyalkylene mono(meth)allyl ether, and polyoxyalkylene Specific examples include polyoxyethylene butyl polyoxyethylene ether, polyoxyethylene propylene polyoxyethylene ether, polyoxyethylene butylene ether, Polyoxyethylene butyl polyoxypropylene ether, polyoxypropylene ethylene ether, polyoxypropylene oxyethylene ether, polyoxyethylene propylene polyoxyethylene monoallyl ether , Polyoxyethylene propylene polyoxyethylene monoallyl ether, polyoxyethylene butyl monoallyl ether, polyoxyethylene butyl polyoxypropylene monoallyl ether, polyoxyethylene propylene monoallyl ether , Polyoxypropylene oxyethylene monoallyl ether, polyoxyethylene butyl polyoxyethylene monovinyl ether, polyoxyethylene propylene polyoxyethylene monovinyl ether, polyoxyethylene butyl Monovinyl ether, polyoxyethylene propylene polyoxyethylene monovinyl ether, polyoxypropylene oxyethylene monovinyl ether, polyoxypropylene oxyethylene monovinyl ether, and the like. Among them, in terms of reactivity or performance, ethers represented by the following general formula (III) can be further preferably used. As a specific example of the polyoxyalkylene ether represented by the general formula (III), polyoxyethylene butylene polyoxyethylene alkenyl ether can be cited.

(In the general formula (III), R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , m, and n are the same as the general formula (II) above).

Examples of vinyl ester monomers include vinyl formate, vinyl propionate, vinyl valerate, vinyl decanoate, vinyl laurate, vinyl stearate, and vinyl benzoate in addition to vinyl acetate. Esters, vinyl pivalate and versatic acid vinyl esters, etc.

The method for deriving organic acid units is not particularly limited, and it can be preferably used: vinyl ester monomers and acrylic acid, methacrylic acid, crotonic acid, maleic acid, etc. which can be copolymerized with vinyl ester monomers A method of copolymerizing saturated carboxylic acid or its salt, olefin sulfonic acid or its salt such as vinyl sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid, etc. In addition, it can be preferably used: after copolymerization with unsaturated carboxylic acid alkyl esters such as dimethyl maleate and monomethyl maleate, saponification is carried out to derive organic acid units (here, carboxyl Acid) method.

The temperature when the vinyl ester-based monomer is copolymerized is not particularly limited, but is preferably 0°C or higher and 200°C or lower, more preferably 30°C or higher and 150°C or lower. When the temperature for the copolymerization is lower than 0°C, a sufficient polymerization rate cannot be obtained, so it is not good. In addition, when the polymerization temperature is higher than 200°C, it is difficult to obtain the target PVA. As a method of controlling the temperature to be used at the time of copolymerization from 0°C or higher to 200°C or lower, a method of controlling by an external sleeve using a suitable heat medium such as water, etc., can be cited.

The polymerization method used for the copolymerization may be any of batch polymerization, semi-batch polymerization, continuous polymerization, and semi-continuous polymerization. As the polymerization method, any method can be adopted from known methods such as a bulk polymerization method, a solution polymerization method, a suspension polymerization method, and an emulsion polymerization method. Among them, a solution polymerization method or a bulk polymerization method in which polymerization is carried out in the presence of an alcohol solvent or without a solvent can be preferably used, instead of the modified species used, most of them have water solubility or influence on the particle size of the polymerization. Interfacial activity therefore requires suspension polymerization and emulsion polymerization to control the particle size of the polymerization. As the alcohol solvent used in the bulk polymerization method or the solution polymerization method, methanol, ethanol, isopropanol, etc. can be used, but it is not limited to these. In addition, these solvents may be used alone, or two or more of them may be used in combination.

The polymerization initiator for radical polymerization of vinyl ester monomers is not particularly limited, and the following compounds can be used alone or in combination of two or more: azobisisobutyronitrile, azobis-2,4- Azo compounds such as dimethylvaleronitrile, azobis(4-methoxy-2,4-dimethylvaleronitrile), azobisdimethylvaleronitrile, azobismethoxyvaleronitrile, etc. Acetyl oxide, benzyl peroxide, lauryl peroxide, acetylcyclohexylsulfonyl peroxide, 2,4,4-trimethylpentyl-2-peroxyphenoxy acetate, etc. Compounds, percarbonate compounds such as diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, diethoxyethyl peroxydicarbonate, tert-butyl peroxyneodecanoate, Perester compounds such as α-cumyl peroxyneodecanoate, etc.

In addition, when the copolymerization is carried out at a high temperature, the coloration of PVA caused by the decomposition of the vinyl ester monomer may be seen. In this case, in order to prevent coloring, an antioxidant like citric acid may be added to the polymerization system at a level of 1 ppm or more and 100 ppm or less (relative to the mass of the vinyl ester monomer).

The saponification method when manufacturing the modified PVA of the present invention is also not particularly limited, and it is preferable to use alcohols in a form that also serves as a solvent according to a conventional method for the polymer obtained by the aforementioned method. Examples of alcohols include methanol, ethanol, butanol, and the like. The concentration of the polymer in the alcohol can be selected from the range of 20% by mass to 50% by mass. As the alkali catalyst, sodium hydroxide, potassium hydroxide, sodium methoxide, sodium ethoxide, potassium methoxide and other alkali metal hydroxides or alkoxide-like alkali catalysts can be used. As acid catalysts, hydrochloric acid, sulfuric acid, etc. can be used The inorganic acid aqueous solution, p-toluenesulfonic acid and other organic acids. The amount of these catalysts used must be 1 millimolar equivalent to 100 millimolar equivalent with respect to the vinyl ester monomer. In this case, the saponification temperature is not particularly limited, and it is preferably generally in the range of 10°C to 70°C, and preferably selected from the range of 30°C to 50°C. The reaction system is usually carried out for 0.5 hour to 3 hours.

The dispersion stabilizer for suspension polymerization of the present invention may contain PVA other than the above-mentioned modified PVA or various other additives within a range that does not impair the gist of the present invention. Examples of the additives include: polymerization regulators such as aldehydes, halogenated hydrocarbons, and mercaptans; polymerization inhibitors such as phenol compounds, sulfur compounds, and N-oxide compounds; pH regulators; crosslinking agents; preservatives; Anti-mold agent, anti-blocking agent; defoaming agent, etc. From the viewpoint of remarkably exerting the effects of the present invention, the dispersion stabilizer for suspension polymerization of the present invention preferably contains 10% by mass or more of modified PVA, more preferably 30% by mass or more, and even more preferably 70% by mass %the above.

The dispersion stabilizer for suspension polymerization of the present invention is particularly preferably used for suspension polymerization of vinyl compounds. Examples of vinyl compounds include: ethylene halide such as vinyl chloride; vinyl esters such as vinyl acetate and vinyl propionate; acrylic acid, methacrylic acid, and esters and salts of these acids; maleic acid, fumaric acid, and one of these acids Esters and acid anhydrides; styrene, acrylonitrile, vinylidene chloride, vinyl ether, etc. Among them, the dispersion stabilizer for suspension polymerization of the present invention can be particularly preferably used in suspension polymerization of vinyl chloride alone or in suspension polymerization of vinyl chloride and a monomer copolymerizable with vinyl chloride. Examples of monomers that can be copolymerized with vinyl chloride include vinyl esters such as vinyl acetate and vinyl propionate; (meth)acrylates such as methyl (meth)acrylate and ethyl (meth)acrylate; ethylene , Propylene and other α-olefins; maleic anhydride, itaconic acid and other unsaturated dicarboxylic acids; acrylonitrile, styrene, vinylidene chloride, vinyl ether, etc.

The dispersion stabilizer for suspension polymerization of the present invention may be used alone or in combination with other stabilizers such as cellulose derivatives and surfactants.

By using the dispersion stabilizer for suspension polymerization of the present invention, a vinyl chloride resin with high volume density of resin particles, uniform particle size distribution, and very excellent physical properties can always be obtained. Hereinafter, the polymerization method of the ethylene-based compound will be described specifically, but it is not limited to these.

In the case of manufacturing vinyl chloride resin particles and other vinyl compound resin particles, with respect to the vinyl compound monomer, 0.01% to 0.3% by mass, preferably 0.04% to 0.15% by mass of the above-mentioned dispersion for suspension polymerization is added relative to the monomer of the vinyl compound stabilizer. In addition, the ratio of the ethylene-based compound to water can be ethylene-based compound:water=1:0.9 to 1:3 in terms of mass ratio, preferably ethylene-based compound:water=1:1 to 1:1.5.

The polymerization initiator can be the polymerization initiator previously used for the polymerization of vinyl compounds, among which the following compounds can be used alone or in combination: diisopropyl peroxydicarbonate, di-2-ethyl peroxydicarbonate Percarbonate compounds such as hexyl hexyl ester and diethoxyethyl peroxydicarbonate, perester compounds such as t-butyl peroxyneodecanoate and α-cumyl peroxyneodecanoate, acetyl peroxide Peroxides such as cyclohexyl sulfonate, 2,4,4-trimethylpentyl-2-peroxyphenoxy acetate, azobis-2,4-dimethylvaleronitrile, azobis Azo compounds such as (4-methoxy-2,4-dimethylvaleronitrile), and further such as potassium persulfate, ammonium persulfate, and hydrogen peroxide.

Furthermore, a polymerization regulator, a chain transfer agent, a gelation modifier, an antistatic agent, a pH regulator, etc. suitable for the polymerization of a vinyl compound can be optionally added.

The feeding ratio of each component, the polymerization temperature, etc. when the polymerization of the vinyl compound is carried out may be determined based on the conditions previously adopted for the suspension polymerization of the vinyl compound, and there is no reason for particular limitation. [Example]

Hereinafter, the present invention will be explained in more detail with examples. [Example 1] 1220 g of vinyl ester, 1150 g of methanol, 1.6 g of dimethyl maleate, polyoxyalkylene alkenyl ether represented by general formula (III) as a modified species and m=5 to 9 and n=45 to 55 (Monomer A: Commercial product) 151 g was fed into the polymerization tank, and the system was replaced with nitrogen for 30 minutes. Regarding the monomer A, m=5-9 and n=45-55 were confirmed by NMR. 0.3 g of azobisisobutyronitrile was fed into the polymerization tank, and 900 mL of a solution obtained by mixing vinyl acetate, methanol, and dimethyl maleate in a mass ratio of 40:58:2 was added dropwise. The polymerization was carried out at 60°C for 11 hours, then the dropwise addition was stopped, and the polymerization was stopped by cooling. Then the unreacted vinyl ester is removed by a conventional method, and the modified vinyl ester polymer obtained is saponified with sodium hydroxide by a conventional method, and then acetic acid is added to produce a dispersion stabilizer with -COOH and -COONa . The viscosity average degree of polymerization, saponification degree, and modification rate of the dispersion stabilizer obtained were measured by the above-mentioned analysis method. As a result, the viscosity average degree of polymerization was 750, the saponification degree was 72 mol%, and the alkylene modification rate was 0.19mol%, the modification rate of organic acid is 0.92mol%.

[Evaluation of Tumbling Point] Prepare a 4% by mass aqueous solution of the dispersion stabilizer obtained above, take about 5 cc into a glass test tube, put the thermometer into the measurement solution while stirring it while raising the temperature to make the measurement solution cloudy, and then slowly cool it while stirring. Take the temperature at which the measurement solution completely becomes transparent, and use this temperature as the tipping point. As a result, the transient point was 45°C.

[Suspension Polymerization of Vinyl Chloride] In a 30L stainless steel autoclave equipped with a stirrer, 12 kg of water at 30°C, 4.0 g of the dispersion stabilizer obtained above, and tert-butyl peroxyneodecanoate 4.6 as a polymerization initiator were fed with stirring. g. 1g of α-cumyl peroxide neodecanoate. After the autoclave was vacuum degassed, 5 kg of vinyl chloride monomer was added, and polymerization was carried out at 57° C. for 4 hours.

[Evaluation of vinyl chloride resin] The average particle size, particle size distribution and volume specific gravity of the obtained vinyl chloride resin were evaluated by the following methods.

The average particle size is measured according to JIS Z8815:1994, using 60 mesh (mesh 250μm), 80 mesh (mesh 180μm), 100 mesh (mesh 150μm), 150 mesh (mesh 106μm), 200 mesh (mesh mesh) 75μm) sieve, the cumulative frequency 50% (quality basis) particle size (D50) as the average particle size, the cumulative frequency 80% (mass standard) particle size (D80) and cumulative frequency 20% (quality basis) The difference in particle size (D20) is taken as the particle size distribution.

The volume specific gravity is measured in accordance with JIS K6720-2:1999.

[Example 2] Except that the monomer A was changed to 101 g, a modified vinyl ester polymer was obtained in the same manner as in Example 1, and then saponified with sodium hydroxide to prepare a dispersion stabilizer. The viscosity average polymerization degree, saponification degree, modification rate, and tipping point of the obtained dispersion stabilizer were measured by the above-mentioned analysis method. In addition, except that the obtained dispersion stabilizer was used, suspension polymerization of vinyl chloride was carried out under the same conditions as in Example 1, and evaluation was performed.

[Example 3] Regarding the modified vinyl ester polymer obtained in Example 2, the amount of sodium hydroxide was adjusted to perform saponification, thereby obtaining a modified vinyl alcohol polymer dispersion stabilizer with a saponification degree of 76%. The viscosity average polymerization degree, saponification degree, modification rate, and tipping point of the obtained dispersion stabilizer were measured by the above-mentioned analysis method. Except for using the obtained dispersion stabilizer, suspension polymerization of vinyl chloride was carried out under the same conditions as in Example 1, and evaluation was performed.

[Example 4] 1220 g of vinyl ester, 1350 g of methanol, 2.4 g of dimethyl maleate, polyoxyalkylene alkenyl ether represented by general formula (III) as a modified species and m=5 to 9 and n=15 to 25 (Monomer B: Commercial product) 52 g was fed into the polymerization tank, and the system was replaced with nitrogen for 30 minutes. Regarding the monomer B, m=5-9 and n=15-25 were confirmed by NMR. Feed 0.3 g of azobisisobutyronitrile into the polymerization tank, and add dropwise 900 mL of a solution obtained by mixing vinyl acetate, methanol, and dimethyl maleate in a mass ratio of 45:52:3. The polymerization was carried out at 60°C for 11 hours, then the dropwise addition was stopped, and the polymerization was stopped by cooling. Then, the unreacted vinyl ester is removed by a conventional method, and the obtained modified vinyl ester polymer is saponified with sodium hydroxide by a conventional method to prepare a dispersion stabilizer. The viscosity average polymerization degree, saponification degree, modification rate, and tipping point of the obtained dispersion stabilizer were measured by the above-mentioned analysis method. In addition, except that the obtained dispersion stabilizer was used, suspension polymerization of vinyl chloride was carried out under the same conditions as in Example 1, and evaluation was performed.

[Example 5] 1850 g of vinyl ester, 1000 g of methanol, 1.2 g of dimethyl maleate, and 133 g of monomer B as a modified species were fed into the polymerization tank, and the system was purged with nitrogen for 30 minutes. Feed 0.3 g of azobisisobutyronitrile into the polymerization tank, and add dropwise 800 mL of a solution obtained by mixing vinyl acetate, methanol, and dimethyl maleate in a mass ratio of 45:52:2. The polymerization was carried out at 60°C for 11 hours, then the dropwise addition was stopped, and the polymerization was stopped by cooling. Then the unreacted vinyl ester is removed by a conventional method, and the obtained modified vinyl ester polymer is saponified with sodium hydroxide by a conventional method to produce a dispersion stabilizer. The viscosity average polymerization degree, saponification degree, modification rate, and tipping point of the obtained dispersion stabilizer were measured by the above-mentioned analysis method. In addition, except that the obtained dispersion stabilizer was used, suspension polymerization of vinyl chloride was carried out under the same conditions as in Example 1, and evaluation was performed.

[Example 6] 1680 g of vinyl ester, 1100 g of methanol, 7.3 g of dimethyl maleate, and 130 g of monomer A as a modified species were fed into the polymerization tank, and the system was purged with nitrogen for 30 minutes. Feed 0.3 g of azobisisobutyronitrile into the polymerization tank, and add dropwise 820 mL of a solution obtained by mixing vinyl acetate, methanol, and dimethyl maleate in a mass ratio of 64:28:8. The polymerization was carried out at 60°C for 11 hours, then the dropwise addition was stopped, and the polymerization was stopped by cooling. Then the unreacted vinyl ester is removed by a conventional method, and the obtained modified vinyl ester polymer is saponified with sodium hydroxide by a conventional method to produce a dispersion stabilizer. The viscosity average polymerization degree, saponification degree, modification rate, and tipping point of the obtained dispersion stabilizer were measured by the above-mentioned analysis method. In addition, except that the obtained dispersion stabilizer was used, suspension polymerization of vinyl chloride was carried out under the same conditions as in Example 1, and evaluation was performed.

[Example 7] Instead of monomer A, feed 56 g of polyoxyethylene glycol allyl ether (monomer C) (Uniox PKA-5005 provided by NOF Corporation) with n=15 to 25 into the polymerization tank. In addition, with In Example 1, a dispersion stabilizer was produced in the same manner. Regarding the monomer C, n=15-25 was confirmed by NMR. The viscosity average polymerization degree, saponification degree, modification rate, and tipping point of the obtained dispersion stabilizer were measured by the above-mentioned analysis method. In addition, except that the obtained dispersion stabilizer was used, suspension polymerization of vinyl chloride was carried out under the same conditions as in Example 1, and evaluation was performed.

[Example 8] Instead of monomer A, polyethylene glycol polypropylene glycol allyl ether (monomer D) (Unilube PKA provided by NOF Corporation) represented by general formula (III) and m=15 to 25 and n=15 to 25 -5013) A dispersion stabilizer was produced in the same manner as in Example 1 except that 74 g was fed into the polymerization tank. The viscosity average polymerization degree, saponification degree, modification rate, and tipping point of the obtained dispersion stabilizer were measured by the above-mentioned analysis method. In addition, except that the obtained dispersion stabilizer was used, suspension polymerization of vinyl chloride was carried out under the same conditions as in Example 1, and evaluation was performed.

[Comparative Example 1] 1600 g of vinyl ester, 860 g of methanol, and 151 g of monomer A were fed into the polymerization tank, and the system was purged with nitrogen for 30 minutes. 0.3 g of azobisisobutyronitrile was fed into the polymerization tank, and after performing polymerization at 60°C for 9 hours, the polymerization was stopped by cooling. Then the unreacted vinyl ester is removed by a conventional method, and the obtained modified vinyl ester polymer is saponified with sodium hydroxide by a conventional method to produce a dispersion stabilizer. The viscosity average polymerization degree, saponification degree, modification rate, and tipping point of the obtained dispersion stabilizer were measured by the above-mentioned analysis method. In addition, except that the obtained dispersion stabilizer was used, suspension polymerization of vinyl chloride was carried out under the same conditions as in Example 1, and evaluation was performed.

[Comparative Example 2] 1220 g of vinyl ester, 1150 g of methanol, and 1.6 g of dimethyl maleate were fed into the polymerization tank, and the system was purged with nitrogen for 30 minutes. 0.3 g of azobisisobutyronitrile was fed into the polymerization tank, and 900 mL of a solution obtained by mixing vinyl acetate, methanol, and dimethyl maleate in a mass ratio of 40:58:2 was added dropwise. The polymerization was carried out at 60°C for 12 hours, then the dropwise addition was stopped, and the polymerization was stopped by cooling. Then the unreacted vinyl ester is removed by a conventional method, and the obtained modified vinyl ester polymer is saponified with sodium hydroxide by a conventional method to produce a dispersion stabilizer. The viscosity average polymerization degree, saponification degree, modification rate, and tipping point of the obtained dispersion stabilizer were measured by the above-mentioned analysis method. In addition, except that the obtained dispersion stabilizer was used, suspension polymerization of vinyl chloride was carried out under the same conditions as in Example 1, and evaluation was performed.

[Comparative Example 3] 3000 g of vinyl ester and 15 g of modified acetaldehyde were fed into the polymerization tank, and the system was replaced with nitrogen for 30 minutes. 0.2 g of azobisisobutyronitrile was fed into the polymerization tank, and after polymerization was performed at 65°C to 75°C for 6 hours, the polymerization was stopped by cooling. Then, according to Example 1, a dispersion stabilizer was produced. The viscosity average polymerization degree, saponification degree, modification rate, and tipping point of the obtained dispersion stabilizer were measured by the above-mentioned analysis method. In addition, except that the obtained dispersion stabilizer was used, suspension polymerization of vinyl chloride was carried out under the same conditions as in Example 1, and evaluation was performed.

[Comparative Example 4] 1600g of vinyl ester, 700g of methanol, and 0.35g of polyethylene glycol monomethacrylate (Blemmer PP-350 provided by NOF Corporation, hereinafter referred to as "monomer E") as modified species were fed into the polymerization Tank, replace the system with nitrogen for 30 minutes. In addition, monomer E was dissolved in methanol to prepare a comonomer solution with a concentration of 5.7% by mass, and nitrogen substitution was performed by bubbling nitrogen. Put 2.5 g of azobisisobutyronitrile into the polymerization tank, add 300 mL of the comonomer solution (dissolve monomer E in methanol with a concentration of 5.7% by mass), and perform polymerization at 60°C for 9 hours. , Cool and stop polymerization. The total amount of methanol added until the polymerization was stopped was 1066 g, and the total amount of monomer E was 22.3 g. Then, in the same manner as in Example 1, a dispersion stabilizer was produced. The viscosity average degree of polymerization, saponification degree, modification rate and tipping point of the obtained dispersion stabilizer were measured by the above-mentioned analysis method. In addition, except that the obtained dispersion stabilizer was used, suspension polymerization of vinyl chloride was carried out under the same conditions as in Example 1, and evaluation was performed. Furthermore, the proton NMR of the obtained dispersion stabilizer was measured, but in the case of polyvinyl alcohol, the peak derived from the modified species observed in the case of polyvinyl ester was not observed. The reason is that the polyoxyalkylene unit is bonded to the polyvinyl alcohol chain via the ester bond, and the polyoxyalkylene unit is detached due to the saponification reaction.

[Table 1-1] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Polyvinyl alcohol used Polyoxyalkylene monomer modified species Polyoxyalkylene ether Polyoxyethylene glycol allyl ether Polyethylene glycol polypropylene glycol allyl ether Modification rate of alkylene group (mol%) 0.19 0.13 0.13 0.12 0.64 0.13 0.12 0.13 n 45 to 55 45 to 55 45 to 55 15 to 25 15 to 25 45 to 55 15 to 25 15 to 25 Part of the number of repeating units n Oxyethylene (R ₁ ＝H, R ₂ ＝H, R ₃ ＝H) Oxyethylene (R ₁ ＝H, R ₂ ＝H, R ₃ ＝H) Oxyethylene (R ₁ ＝H, R ₂ ＝H, R ₃ ＝H) Oxyethylene (R ₁ ＝H, R ₂ ＝H, R ₃ ＝H) Oxyethylene (R ₁ ＝H, R ₂ ＝H, R ₃ ＝H) Oxyethylene (R ₁ ＝H, R ₂ ＝H, R ₃ ＝H) Oxyethylene (R ₁ ＝H, R ₂ ＝H, R ₃ ＝H) Oxyethylene (R ₁ ＝H, R ₂ ＝H, R ₃ ＝H) m 5 to 9 5 to 9 5 to 9 5 to 9 5 to 9 5 to 9 - 15 to 25 Part of the number of repeating units m Oxybutylene (R ₄ ＝H, R ₅ ＝C ₂ H ₅ ) Oxybutylene (R ₄ ＝H, R ₅ ＝C ₂ H ₅ ) Oxybutylene (R ₄ ＝H, R ₅ ＝C ₂ H ₅ ) Oxybutylene (R ₄ ＝H, R ₅ ＝C ₂ H ₅ ) Oxybutylene (R ₄ ＝H, R ₅ ＝C ₂ H ₅ ) Oxybutylene (R ₄ ＝H, R ₅ ＝C ₂ H ₅ ) - Oxypropylene (R ₄ ＝H, R ₅ ＝CH ₃ ) Organic acid Dimethyl maleate Dimethyl maleate Dimethyl maleate Dimethyl maleate Dimethyl maleate Dimethyl maleate Dimethyl maleate Dimethyl maleate Organic acid modification rate (mol%) 0.92 0.88 0.88 1.20 0.60 2.80 0.86 1.00 Viscosity average degree of polymerization 750 730 730 650 780 800 600 690 Saponification degree (mol%) 72 73 76 72 78 72 73 74 Short point 45 46 63 50 44 88 44 55 Resin physical properties of vinyl chloride Average particle size (μm) 127 143 145 150 135 151 153 144 Particle size distribution (D80-D20) (μm) 49 51 55 57 53 61 60 53 Specific gravity (g/mL) 0.48 0.48 0.50 0.48 0.46 0.52 0.46 0.49 [Table 1-2] Comparative example 1 Comparative example 2 Comparative example 3 Comparative example 4 Polyvinyl alcohol used Polyoxyalkylene monomer modified species Polyoxyalkylene ether no no Polyethylene glycol monomethacrylate Modification rate of alkylene group (mol%) 0.19 - - 0.0 n 45 to 55 - - 6 to 10 Part of the number of repeating units n Oxyethylene (R ₁ ＝H, R ₂ ＝H, R ₃ ＝H) - - Oxyethylene (R ₁ ＝H, R ₂ ＝H, R ₃ ＝H) m 5 to 9 - - - Part of the number of repeating units m Oxybutylene (R ₅ ＝H, R ₆ ＝C ₂ H ₅ ) - - - Organic acid no Dimethyl maleate - Dimethyl maleate Organic acid modification rate (mol%) - 0.80 - 0.80 Other modified species - - Acetaldehyde - Other modification rate (mol%) - - 0.20 - Viscosity average degree of polymerization 730 700 670 750 Saponification degree (mol%) 72 72 71 72 Short point 30 46 31 48 Resin physical properties of vinyl chloride Average particle size (μm) 155 180 171 184 Particle size distribution (D80-D20) (μm) 65 68 89 75 Specific gravity (g/mL) 0.43 0.47 0.44 0.48

Claims (7)

A modified vinyl alcohol polymer having: polyoxyalkylene units, having a part represented by the general formula (I), which is only linked to the polyvinyl alcohol chain via ether bonds and/or carbon-carbon bonds And the organic acid unit is bonded to the polyvinyl alcohol chain; relative to the total moles of monomer units constituting the polyvinyl alcohol chain of the modified vinyl alcohol polymer, it is bonded to the aforementioned polyoxyalkylene unit The ratio of the number of moles of the aforementioned monomer units is 0.01 mol% to 5 mol%, and relative to the total number of moles of the monomer units constituting the polyvinyl alcohol chain of the modified vinyl alcohol polymer, the organic acid unit The ratio of the number of moles is 0.1 mol% to 10 mol%;

(In the formula, R ₁ and R ₂ are each independently a methyl group or an ethyl group or a hydrogen atom, R ₃ is an alkyl group or a hydrogen atom; n represents the number of repeating units, and is an integer of 5≤n≤70). The modified vinyl alcohol polymer according to claim 1, wherein at least a part of the aforementioned polyoxyalkylene unit has a part represented by the general formula (II);

(In the formula, R ₁ , R ₂ , R _{3 are} as described in claim 1; one of R ₄ and R ₅ is a methyl group or an ethyl group, and the other is a hydrogen atom; m represents the number of repeating units, and is 1≤m≤ An integer of 30; where the part of the number of repeating units n is different from the part of the number of repeating units m). The modified vinyl alcohol polymer according to claim 1 or 2, wherein the organic acid unit has a carboxylic acid ester. The modified vinyl alcohol polymer described in claim 1 or 2 has an average viscosity of 500 to 4000 and a saponification degree of 70 mol% or more. A dispersion stabilizer for suspension polymerization, which contains the modified vinyl alcohol polymer as described in claim 1 or 2. A method for producing a vinyl resin, comprising: using a dispersion stabilizer for suspension polymerization as described in claim 5 to copolymerize a vinyl compound monomer, or a vinyl compound monomer, and the aforementioned vinyl compound monomer The monomer mixture is dispersed in water for suspension polymerization. A method for producing a modified vinyl alcohol-based polymer is to produce the modified vinyl alcohol-based polymer as described in any one of claims 1 to 4, comprising the following steps: a vinyl ester-based monomer is mixed with an unsaturated organic Under the coexistence of acid, it is copolymerized with the unsaturated monomer having the aforementioned polyoxyalkylene unit to obtain a modified vinyl ester polymer.